From the time you first spray it until dries could take an hour or so but you normally wouldn't be sitting there waiting for it to dry. You'd be working on another project or doing some other chore. I like to pre-wash all my fabric for a specific project at one time. I don't necessariy starch it at one time though--especially not the backing. The backing is done right before I get ready to load it on the frame & that might be weeks, months or for a couple quilts--years--before I choose or piece the backing. It really doesn't take that long for the starch to dry anyway so if you want to sit & wait--you could browse through your patterns or pull fabric for your next project while you wait. It doesn't have to be dry as a bone--just not soaking wet or it will flake and possibly scorch.